It never ceases to surprise me how little the television version of a successful book series will take from the source material. Take Rizzoli & Isles, a series airing on Showtime, and one that we watch and enjoy here.

Aside from the names and occupations of the main characters and the fact that the show is set in Boston (although they don’t film it there) there isn’t a great deal of similarity.

TV’s Jane Rizzoli is far better looking and way more self-confident than the one in the books. Gerritsen’s character has been obsessed with making it as a woman in the man’s world of the police force, but the TV version seems to do this flawlessly. Oh, and in the books (this being the fourth in the series) Rizzoli is married to an FBI agent and eight months pregnant.

Maura Isles is an odd combination of brilliant and socially awkward in the show. She was adopted into a wealthy family and is clearly a social class above her BPD peers. Sometime last season we learned her birth father was a mobster. This season we learned her mother gave her up at birth, but they have reconnected. Gerritsen’s character was also adopted, but had a twin sister she never knew about and is the offspring of a – oh, I can’t tell you that yet. You have to read the book.

Pregnant ladies are definitely a factor in this book, but so is Isles’ personal history. She arrives back from a conference in Europe to find her driveway full of squad cars and everybody doing double takes when she walks from her cab to the house. A car parked in her driveway contains the body of a woman who is her spitting image, and everyone thought she had been murdered until she walked into her yard.

Forensic examination reveals that they are sisters. As things develop it emerges that this other woman, Anna Leoni, had apparently had the same curiosity about her origins that Maura has always had and has been digging into her past. Clearly, she had got far enough to discover that Maura existed. She also had an abusive husband she was trying to hide from.

Was it the husband that killed her, or did her digging unearth secrets that someone wanted to keep hidden? It’s something Isles needs to know, and so she begins to investigate the life of her dead sister, retracing her footsteps until the trail leads her to the house where their mother must have lived as a child and to the beginnings of finding out where she and Anna came from.

Their mother, Amalthea Lank, is still serving time for the brutal murder of two women. Lank appears to everyone to be hopelessly insane, schizophrenic to the extent that she has lost contact with the world.

While all this is going on, Jane and the other detectives in the homicide squad are investigating a series of bizarre murders in which pregnant woman have been kidnapped quite far along in their pregnancies, kept until they came to term and then murdered by Caesarian section, with the babies being sold.

For Jane, well along in her pregnancy, this is a particularly difficult case to deal with, and every lead they track down seems to presage a new and gruesome murder, as the perpetrators do their best to snuff anything that might lead the authorities to them.

What I haven’t mentioned so far is the ticking clock aspect of this mystery. The killers’ latest victim is Mattie Purvis, taken in chapter five. She spends most of the story in a box, underground, kept alive on a ration of junk food and water, revisited every few chapters by the kidnapper, who wants to know if she’s alright. What does he want from her? It doesn’t make her feel any better when she suddenly figures it out, but it does make her determined.

The book is fairly evenly divided between the two main characters, who are not nearly as chummy on paper as they are on the small screen. There is a relationship building there and a lot of mutual respect, but they each have too many buried emotions to be really comfortable sharing to the degree that their television counterparts do.

If you pick up one of these books looking for the same sort of ensemble cast you’ve seen on television, you won’t find that. You will find some pretty good mysteries with characters that are developing as the series progresses.